Parenteral Delivery: Under Control

INTRODUCTION

The latest craze to sweep the pharmaceutical industry is one of controlled-release drug delivery systems. 

This controlled release can be systemic (generally via the bloodstream), as is generally the case for oral preparations, or act specifically at the site of greatest benefit (for example, in implanted devices) and these dosage forms are defined as preparations that modify the rate and/or the time and/or site of release of the active ingredient, in order to achieve specific therapeutic objectives which cannot be achieved with conventional dosage forms similarly administered.

The science of controlled release has become a research discipline whose future depends on a thorough understanding of the interactions between the delivery system and the biological or environmental barriers to delivery of active substances. In terms of patient care, the objective may be to prolong the duration of action of an active agent, to minimise adverse reactions, or to maximise efficacy. This objective may be achieved by control of diffusion, reaction rates or other physicochemical parameters through the use of rate-controlling materials, manipulation of the appropriate biological barriers, targeting, or manipulation of the fate of the therapeutic agent once beyond these barriers.

On the business end, controlled release dosages are attractive because they afford ethical manufacturers a means of extending patent coverages, and permit generic companies to develop competitive products. They could also be instrumental in improving formulations of nutritional supplements, developing economical veterinary medicines, and, particularly in Asian countries, modernising dosage forms of traditional herbal medicines. Targeting a specific delivery site is an important aspect of achieving these patient administration and commercial gains.

DEVELOPING A CONTROLLED RELEASE PRODUCT

If a company wants to formulate a CR version of an established IR (immediate release) drug the proposed new dosage form needs to be treated more or less as a new compound, a new development project.

The scientists will first look at the product's physical and chemical characteristics to make sure it is, in fact, a good candidate for controlled release. Scientists need to choose the right components and assure their compatibility with a diverse selection of new drug substances. 

This often entails long-term partnering between manufacturing companies and suppliers of functional excipients and delivery technologies. Functional testing of polymers and other excipients to predict performance in a final dosage form could be performed by QA/QC labs performing incoming raw material screening, or used as a screening or qualification tool by product formulators.

An ideal functional test would correlate or predict that a specific polymer batch functions in a way that contributes to the desired overall performance of the final/finished dosage form. The challenge with this type of testing is trying to get a general assessment of a polymer's performance when it will be used for a particular purpose in a specific customer application. 

Whilst there are several major routes for the administration of drugs, the following probes, fixtures and methods presented and outlined represent a non-exhaustive summary of the currently available and potentially invaluable solutions for the assessment of the physical properties of pulmonary, parenteral, ocular, vaginal and rectal controlled release products.

There is a Texture Analysis test for virtually any physical property. Contact Stable Micro Systems today to learn more about our full range of solutions.

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